In the demolition of iron-or steel-reinforced concrete structures, a reinforcement cutter attached to a power shovel is generally employed. Regarding the reinforcement cutter, the following proposal has been made, for instance. (cf. Japanese Patent Publication No. 62-17059).
This cutter comprises a couple of jaws which are opposedly disposed and adapted to relatively swing to open and close between a pair of side plates, with bases of the respective jaws being connected to a hydraulic cylinder, a swivel member consisting of a swivel end plate and a locking end plate as attached to bases of said side plates, said jaws being provided with shearing cutters on mutually opposed inner sides thereof along the longitudinal direction thereof (front and back as viewed from the operator), crushing cutters of lower profile than said shearing cutters in positions forwardly of said shearing cutters, said crushing cutters being configured in the shape of the capital letter V in sectional view and not intersecting each other when the jaws are closed, and intermeshing stop means adapted to prevent lateral dislodging of the cutting work as disposed further forwardly of said crushing cutters.
Therefore, in the proposed reinforcement cutter, the cutting work such as a steel reinforcement is first crushed by the crushing cutters and, then, the jaws are advanced to cut the crushed work with the shearing cutters. In case the cutting work is a thin member, the work is partially entrapped between the cooperating shearing cutters to expand the lateral clearance of these cutters, that is to say a lateral cutter displacement takes place but, to prevent this displacement, the juxtaposed jaws are interlocked with each other.
Although the lateral displacement of shearing cutters in cutting is precluded in such proposed reinforcement cutter, the cutting work tends to slide forwards or towards the low-profile crushing cutters in the shearing phase so that the proposed cutter has the disadvantage that it can be applied only to easily crushable small-sized work.
On the other hand, Japanese Kokai Patent Application No. 57-18461 discloses a reinforcement cutter comprising a stationary jaw and a movable jaw which are opposedly disposed to open and close, said stationary jaw having a longitudinally extending slit while said movable jaw having a curved hook forwardly of its shearing cutter so that when said hook is engaged with said slit prior to cutting, not only the lateral displacement of the shearing cutters but also the forward slide of the work is prevented. In other words, this reinforcement cutter grips the work and cuts it.
However, inasmuch as the above reinforcement cutter grips the work securely by the hook and slit means and cuts the work in that constrained condition with the shearing cutters, the forward slide of the work applies a destructively excessive force to the hook when the rigidity of the work is high, so that the cutter can be applied only to the cutting of small beams, pipes, cables and the like.
As apparent from the foregoing review of the prior art, the conventional reinforcement cutter construction has little room for any remarkable improvement in cutting performance and cannot deal with unpredicted jobs such as cutting of unusually tough structural members.